Atrial fibrillation (AF) is a major cause of stroke and the most common arrhythmia that is clinically significant, with prevalence rates of 3.8% in individuals 60 years of age or older and 9.0% in individuals over 80 years of age. In 2001, the prevalence of AF was projected to increase 2.5-fold by 2050 due to the rapidly growing elderly population. One surgical treatment method for AF is called the maze procedure, which was developed in 1991 by Cox. In this procedure, incisions are made directly into the atrium of the heart during major, open heart surgery. While successful, due to the procedure's long operative time and morbidity rate, most clinicians have adopted a variation of the procedure which uses percutaneous radiofrequency ablation (RFA) to create transmural lines of electrically inactive scar tissue within the left atrium (LA), endocardially. As a result, there has been an increase in RFA techniques to treat paroxysmal and persistent atrial fibrillation. The approach to RFA changed dramatically in 1998 with the discovery by Haïssaguerre and associates that the majority of ectopic atrial beats originated somewhere within 1 or more of the 4 pulmonary veins (PVs) due to the extension of muscular bands from the LA into the PVs. Following this discovery, mapping and ablation of arrhythmogenic foci of both the PVs and the LA have been performed, with today's procedures showing success rates of 60-90%.
Although RFA has been effective at treating atrial fibrillation, complications have been reported, the most serious of which is a left atrial-esophageal fistula that forms secondary to thermal esophageal injury. Atrio-esophageal fistula is the most dreadful and lethal complication among all others related to AF catheter ablation. Patients with an atrio-esophageal fistula may be presented with a variety of signs and symptoms such as chest pain, heartburn, dysphagia, anorexia, and hematemesis immediately after or also late after the index procedure. Usually death occurs because of cerebral or myocardial air embolism, endocarditis, massive gastrointestinal bleeding and septic shock. New esophageal late gadolinium enhancement has been shown to be present in almost one-third of patients after AF ablation, suggesting some form of esophageal injury. This finding is irrespective of the type of catheter ablation (irrigated vs. not-irrigated tip) used during the procedure, of ablation time, of anatomical location of the esophagus compared with the left atrium, of the size of left atrium cavity or of the timing of cardiac magnetic resonance study after pulmonary vein isolation.
As demonstrated by computed tomography, cardiac magnetic resonance, and intracardiac echocardiography, the strict anatomic relationship between the left atrium and the esophagus together with the delivery of radiofrequency energy on the posterior wall of the left atrium are the principal causes leading to the occurrence of atrio-esophageal fistula or, more generally, of esophageal injury.
Since radiofrequency energy exerts a rise in local temperatures, it is common practice now to monitor the esophageal temperature with an esophageal probe to titrate the radiofrequency energy application on the areas at potential risk of esophageal injury and to stop radiofrequency energy delivery when a rapid elevation of the esophageal internal temperature is recorded. However, a problem with current systems and methods for measuring and monitoring intracavitary tissue temperature is poor correlation between esophageal internal temperature and total radiofrequency energy delivery.
For example, in U.S. Patent Pub. No. 2014/0012155 to Flaherty, a device having a plurality of sensors is used to monitor temperature of esophageal tissue while actively ablating target tissue to reduce risk of injury to untargeted tissues. The device may be positioned within the esophagus with positioning elements. However, the accuracy of esophageal temperature monitoring to estimate the esophageal heating and then anticipating the formation of the esophageal injury is uncertain. For example, particles, fluids and gases traversing the esophagus may obstruct the field of view of the sensors, resulting in inaccurate temperature measurements.
It would therefore be desirable to provide improved systems and methods for measuring and monitoring intracavitary tissue temperature.
Specifically, it would be desirable to provide systems and methods for measuring and monitoring intracavitary tissue temperature using a device tailored for optimal introduction to, positioning at, and having an optimum, unobstructed field of view of, the target tissue.